Tracking of body fluid loss during surgery is still done largely manually, as is accounting for sponges which have been utilized to absorb body fluids. Fluid loss must be tracked continually during a procedure in order to avoid underestimating (or overestimating) the number of units of blood or other fluid that must be administered to a patient for replacement of the lost fluid. Underestimation and overestimation carry attendant risks that are well known in the field.
Conventional fluid tracking techniques require that sponges containing body fluids be laid out on a fabric or plastic sheet or otherwise arranged in plastic bags or pockets where they can be inspected, sorted, counted, and contained for disposal. This handling task typically and ultimately falls upon the circulating nurse. The anesthesiologist or anesthetist visually estimates the quantity of blood and fluid in the sponges. The anesthesia staff typically simply look at the sponges and make their best estimate.
Conventional estimation of bodily fluid loss from sponge examination is accordingly an anachronism. Conventional wisdom holds, for instance, that anesthesiologists and surgeons tend to underestimate blood loss in the sponges. This is in great part due to the limited access to (and visibility of) the contaminated surgical sponge and to the dilution of the blood in the sponge by irrigant or body fluids. Evaporation of the sponge contents into the operating room air and absorption of fluids by surrounding materials (such as surgical drapes) further confuse the estimate.
Apart from fluid tracking issues, an accurate sponge count at the end of surgical procedures is also necessary in order (among other things) to ensure that no sponges have been left in the patient. Accordingly, sponges are conventionally counted manually during and at the end of a surgical procedure by the circulating nurse. Sometimes multiple counts are required for comfort and accuracy. The acts of counting and accounting require considerable handling, thus increasing the risk of transcutaneous biocontamination.
Blood and other body fluids have recently been considered to be biocontaminants that require careful handling, management and control because of the viral, bacterial, and other infectious agents they may contain. Laying the sponges out on plastic floor-sheets to account for blood loss, like other earlier techniques, is thus increasingly considered to be unacceptable. It is becoming more and more desirable in addition to dispose of items or articles, such as sharps and sponges, used during invasive procedures, in specifically marked, biohazard containers. Such containers have fluid-tight seals that limit the risk of contamination of the nurse or other user.
Devices for tracking body fluid loss and for displaying sponge counts during surgical procedures are available in the marketplace. U.S. Pat. No. 4,449,538 issued May 22, 1984 and entitled "Medical-Electronic Body Fluid Accounting System" and U.S. Pat. No. 4,922,922 issued May 8, 1990 to Pollock, et al. for a "Fluid Monitoring Apparatus" (both are incorporated herein by this reference) disclose devices that more accurately and safely monitor blood and body fluids in a patient. One device disclosed in the Pollock, et al. patent, for instance, employs a load cell that supports a container for receiving various sizes of sponges that contain such fluids. The sponges may be sorted by passing them through a disposable sorting grid located above, or forming a part of, a receptacle. Photoelectric or other sensors detect the cumulative number of sponges placed into the container via each opening in the sorting grid. The load cells and sensors are connected to controller circuitry. The controller counts, tracks, and displays the cumulative number of sponges of each size that pass the sensors and fall into the container; this controller also tracks the cumulative weight and calculates (using standard weight-to-volume ratios) and displays the cumulative volume of fluid in the sponges.
The use of a container that simply rests atop a surface supported by a number of load cells, such as those disclosed in the above-referenced Pollock, et al. patent, creates weighing inaccuracies, however. Malposition of the container on the surface, movement of the container (as sponges are placed in it or as the apparatus is moved during surgery), and the inherent plurality of the load cells are among the causes of such inaccuracies.
Additionally, a flexible container, such as a bag or other flexible receptacle that may be inexpensively manufactured and conveniently provided to receive the sponges, would be more desirable than the rigid receptacle first proposed. Such flexible receptacles would obviously collapse if placed atop a platform (such as shown in the above-referenced patent). Further, when rigid structure was added to the platform, ensuring that the receptacle would remain upright, the device became difficult to clean and maintain, and ultimately unsafe.
In order to decrease the potential for errors in the weighing, counting and tracking process and for initiating clinical malresults, human intervention should be minimized. For instance, it would be desirable to have the device automatically detect the presence or absence of a sorting receptacle, so that the apparatus could automatically tare the weight of the container without being instructed to do so by the human operator. Similarly, it would be preferable to have apparatus that automatically detects when one container has been removed and another replaced, rather than depending on the operator to push a button or sequence of buttons in order for the apparatus to recognize that removal or replacement has occurred. It would further be preferable to have the apparatus sense a blockage of the sensors, or detect the existence of other abnormal conditions, allowing the informed user to make necessary corrections to the tracking, sorting, and counting and weighing data. The desirability of automated apparatus functions is magnified when one considers the stressful and hurried environment characterized by some surgical procedures.